Apparatus and method for manufacturing a wafer

ABSTRACT

Various embodiments provide an apparatus and method for fabricating a wafer, such as a SiC wafer. The apparatus includes a support having a plurality of arms for supporting a substrate. The arms allows for physical contact between the support and the substrate to be minimized. As a result, when the substrate is melted, surface tension between the arms and molten material is reduced, and the molten material will be less likely to cling to the support.

BACKGROUND Technical Field

The present disclosure is directed to an apparatus and method forfabricating semiconductor wafers.

Description of the Related Art

Semiconductor devices are typically fabricated in silicon wafers.However, silicon carbide (SiC) wafers have become increasing populardue, at least in part, to the chemical-physical properties of SiC. Forexample, SiC generally has a higher band gap than silicon. As a result,SiC, even at relatively small thicknesses, has a higher breaking voltagecompared to silicon. Accordingly, SiC is desirable for applications thathave high voltages, such as power applications.

SiC may occur in a number of different chrystallographic structures orpolytypes. The most common polytypes are the cubic polytype (3Cpolytype), the hexagonal polytype (4H and 6H polytypes), and therhombohedric polytype (15R polytype). 3C SiC wafers possess uniqueproperties in comparison other wafer polytypes. For example, 3C SiCwafers generally have lower density of traps and/or higher channelelectron mobility than 4H SiC wafers.

BRIEF SUMMARY

The present disclosure is directed to an apparatus and method forfabricating a semiconductor wafer, such as a silicon carbide (SiC)wafer.

According to one embodiment, the apparatus includes a body, a heater, aninput duct, an output duct, a support, and a receptacle. The support ispositioned on the receptacle and in the reaction chamber. The supportincludes a plurality of arms for supporting a substrate or a wafer, suchas a silicon substrate. The arms allows for physical contact between thesupport and the substrate to be minimized. As a result, when thesubstrate is melted, surface tension between the arms and moltenmaterial is reduced, and the molten material will be less likely tocling to the support, itself.

According to one embodiment, a method is used to fabricate a SiC wafer.The method includes positioning a silicon substrate on the support, andforming a first layer of silicon carbide on the silicon substrate byexposing the silicon substrate to a flow of precursors (i.e.,hetero-epitaxy). The silicon substrate has a first melting temperatureand the silicon carbide has a second melting temperature that is higherthan the first melting temperature. The method further includes heatingthe reaction chamber to a temperature that is higher than the firstmelting temperature and lower than the second melting temperature suchthat the silicon substrate begins to melt. The melted silicon substratedrains through an opening in the support and into the receptacle. Thetemperature of the reaction chamber is maintained until the first layerof silicon carbide is substantially separated from the siliconsubstrate. Simultaneously with or subsequent to the melting of thesilicon substrate, the first layer of silicon carbide is exposed to aflow of precursors to form a second layer of silicon carbide (i.e.,homo-epitaxy). Once the second layer of silicon carbide reaches adesired thickness, any remaining portions of the silicon substratecoupled to the first layer of silicon carbide is removed by an etchingprocess.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an apparatus according to anembodiment of the present disclosure.

FIG. 2 is a perspective view of a support according to an embodiment ofthe present disclosure.

FIG. 3 is a plan view of the support of FIG. 2.

FIG. 4 is a cross-sectional view of the support along the axis shown inFIG. 3.

FIG. 5 is a cross-sectional view of the support along the axis shown inFIG. 3.

FIG. 6 is an enlarged perspective view of an arm of the support of FIG.2.

FIG. 7 is an enlarged plan view of the arm of FIG. 6.

FIG. 8 is an enlarged cross-sectional view of the arm along the axisshown in FIG. 7.

FIGS. 9 to 13 are cross-sectional views illustrating various stages of amethod of fabricating a wafer using the apparatus of FIG. 1 according toan embodiment disclosed herein.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments of thedisclosure. However, one skilled in the art will understand that thedisclosure may be practiced without these specific details. In someinstances, well-known details associated with, for example, reactionchambers, fabrication processes, and/or semiconductor wafers have notbeen described to avoid obscuring the descriptions of the embodiments ofthe present disclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments.

In the drawings, identical reference numbers identify similar featuresor elements. The size and relative positions of features in the drawingsare not necessarily drawn to scale.

One solution for fabricating a silicon carbide (SiC) wafer is disclosedin U.S. patent application Ser. No. 15/715,940, entitled “APPARATUS FORMANUFACTURING A SILICON CARBIDE WAFER”. The fabrication of the SiC waferdisclosed in U.S. patent application Ser. No. 15/715,940 includes, forexample, placing a silicon substrate on a support having a plurality ofbars and openings, growing a 3C-SiC epitaxial layer on the siliconsubstrate, and then separating the silicon substrate from the 3C-SiCepitaxial layer by melting the silicon substrate. The melted silicon isdrained through the plurality of openings in the support and into areceptacle. The inventors have since discovered that the supportdisclosed in U.S. patent application Ser. No. 15/715,940 may not alwaysproperly drain the melted silicon into the receptacle. Rather, theinventors have discovered that the melted silicon may sometimes stick orcling to the support, itself, due to surface tension between the meltedsilicon and the support.

An improved apparatus and method for fabricating a wafer, such as a SiCwafer, are described herein. The apparatus may address one or more ofthe problems associated with the fabrication of a SiC wafer as describedin U.S. patent application Ser. No. 15/715,940.

FIG. 1 is a cross-sectional view of an apparatus 10 according to oneembodiment. The apparatus 10 includes a body 12, a heater 14, an inputduct 16, an output duct 18, a support 20, and a receptacle 22.

The body 12 forms a reaction chamber 24. The reaction chamber 24provides an enclosed space for various reactions to occur. The support20 and the receptacle 22 are positioned within the reaction chamber 24.In one embodiment, the body 12 is made of an insulating material thatthermally insulates the reaction chamber 24 from an externalenvironment.

The heater 14 is coupled to the body 12. The heater 14 heats thereaction chamber 24 and any contents within the reaction chamber 24(e.g., the support 20, the receptacle 22, gases, substrates, wafers, orother various objects). The heating device 14 may be any type of heatingdevice. For example, the heater 14 may be an inductive heater including,for example, a plurality of coils; a resistive heater including, forexample, carbide covered resistors; etc.

The input duct 16 provides a fluidic path from an environment externalto the apparatus 10 and into the reaction chamber 24. In one embodiment,as will be discussed in further detail below with respect to FIGS. 9 to13, the input duct 16 is used to input precursors and gases into thereaction chamber 24.

The output duct 18 provides a fluidic path from the reaction chamber 24and out to an environment external to the reaction chamber 24. In oneembodiment, as will be discussed in further detail below with respect toFIGS. 9 to 13, the output duct 18 is used to discharge reaction gasesfrom the reaction chamber 24.

In one embodiment, the apparatus 10 is a horizontal flux reactionchamber. In this embodiment, as shown in FIG. 1, the input duct 16 andthe output duct 18 are horizontally aligned with each other, and gasesflow longitudinally along, for example, an upper surface of the support20. Other configurations are also possible. For example, in oneembodiment, the apparatus 10 is a vertical flux reaction chamber. Inthis embodiment, the input duct 16 and an output duct 18 are verticallyaligned with each other, and gases flow transverse to, for example, anupper surface of the support 20.

The support 20 is positioned on the receptacle 22 and in the reactionchamber 24. The support 20 provides a platform to receive and holdvarious objects, such as a substrate or a wafer, within the reactionchamber 24. For example, as will be discussed in further detail belowwith respect to FIGS. 9 to 13, a silicon substrate is positioned on thesupport 20 during fabrication of a SiC wafer. The support 20 is oftenreferred to as a susceptor.

As will be discussed in further detail below with respect to FIGS. 2 to8, the support 20 includes a frame 26 positioned on and supported by thereceptacle 22; an opening 28 that provides a drain in which material mayflow through; and a plurality of arms 30 to support, for example, asilicon substrate.

The receptacle 22 is positioned in the reaction chamber 24 and directlyunderlies the support 20. The support 20 rests upon the receptacle 22.The receptacle 22 collects any material that is drained through theopening 28 of the support 20. The receptacle 22 includes a base 32 andsidewalls 34. The base 32 directly underlies the opening 28 and the arms30 of the support 20. The sidewalls 34 directly underlie the frame 26 ofthe support 20. In one embodiment, the sidewalls 34 are in directphysical contact with the frame 26 of the support 20.

FIG. 2 is a perspective view of the support 20 according to anembodiment of the present disclosure. FIG. 3 is a plan view of thesupport 20 according to an embodiment of the present disclosure. FIG. 4is a cross-sectional view of the support 20 along the axis shown in FIG.3 according to an embodiment of the present disclosure. FIG. 5 is across-sectional view of the support 20 along the axis shown in FIG. 3according to an embodiment of the present disclosure. It is beneficialto review FIGS. 2 to 5 together. The support 20 includes the frame 26,the opening 28, and the arms 30.

The frame 26 physically couples the plurality of arms 30 together. Aspreviously discussed with respect to FIG. 1, the frame 26 rests upon thesidewalls 34 of the receptacle 22. The frame 26 may have any shape. Forexample, the frame 26 may be circular or rectangular in shape. In oneembodiment, as best shown in FIG. 3, the support 20 has a circularshape.

The opening 28 is formed in the frame 26. Stated differently, theopening 28 is surrounded and enclosed by the frame 26. The opening 28provides a drain through which material may flow. For example, as willbe discuss in further detail below with respect to FIGS. 9 to 13, asilicon substrate is positioned on the support 20 and is melted anddrained through the opening 28.

The arms 30 are physically coupled to each other by the frame 26, andare cantilevered from the frame 26. In particular, as best shown inFIGS. 1 and 2, each of the plurality of arms has a fixed end attached tothe frame 26; and a free end, which is opposite to the fixed end, thatis suspended over the receptacle 22. In one embodiment, as best shown inFIGS. 2 to 3, the arms 30 extend from the frame 26 towards a center ofthe opening 28. The arms 30 are used to support a substrate or a waferwithin the reaction chamber 24. For example, as will be discussed infurther detail below, a silicon substrate is positioned on the support20 to fabricate a SiC wafer.

In one embodiment, all of the arms 30 may also have the same length. Inanother embodiment, the arms 30 have varying lengths. For example, inone embodiment, the arms 30 include multiple sets of arms with each setof arms having a different length. For example, as best shown in FIGS. 2and 3, the arms 30 include two sets of arms: a first set of arms 36having a first length L1, and a second set of arms 38 having a secondlength L2 that is smaller than the first length L1. By having multiplesets of arms with different lengths, the support 20 is able to supportdifferent sized wafers. For example, referring to FIG. 3, the first setof arms 36 is configured to support a first circular substrate having anoutline 40 with a first radius, and the second set of arms 38 isconfigured to support a second circular substrate having an outline 42with a second radius that is larger than the first radius.

In one embodiment, all of the arms 30 are positioned within the sameplane. For example, as shown in FIGS. 3 to 5, the first set of arms 36and the second set of arms 38 are positioned within the same plane. Inanother embodiment, the arms 30 may have arms positioned in differentparallel planes. For example, in one embodiment, the first set of arms36 are positioned in a first plane, and the second set of arms 38 arepositioned in a second plane that is above and parallel to the firstplane. Stated differently, the second set of arms 38 are positionedabove the first set of arms 36. Having arms positioned in differentplanes minimizes the number of arms that contact a substrate positionedon the support 20. For example, if the second circular substrate havingthe outline 42 is positioned on the second set of arms 38, the secondcircular substrate would not contact the first set of arms 36 as thefirst set of arms 36 are positioned below the second set of arms 38.

In one embodiment, the arms of the multiple sets of arms are positionedin an alternating fashion. For example, as best shown in FIGS. 2 and 3,the first set of arms 36 are alternated with the second set of arms 38around the frame 26.

Although the first set of arms 36 and the second set of arms 38 eachinclude four arms, each of the multiple sets of arms may include anynumber of arms. For example, the first set of arms 36 may include 3, 5,6 or 8 arms.

In one embodiment, the arms 30 are spaced from each other. For example,as best shown in FIGS. 2 to 3, the arms 30 are spaced from each other bythe opening 28. Having the arms 30 spaced from each other ensures thatthe arms 30 do not block or impede material that is drained through theopening 28.

In one embodiment, the arms 30 are spaced from each other bysubstantially equal distances along the frame 26. For example, referringto FIG. 3, the arms 30 are separated by each other by a distance D1along the frame 26.

As previously discussed, in one embodiment, the arms 30 include multiplesets of arms with each set of arms having a different length. In oneembodiment, the arms of each set of arms are spaced from each other bysubstantially equal distances along the frame 26. For example, referringto FIG. 3, the first set of arms 36 may be separated from each other bya second distance D2. Similarly, the second set of arms 38 may beseparated from each other by a third distance D3. In one embodiment, thesecond distance D2 and the third distance D3 are substantially equal toeach other.

As previously discussed, the support disclosed in U.S. patentapplication Ser. No. 15/715,940 may not always properly drain the meltedsilicon into the receptacle. Rather, the inventors have discovered thatthe melted silicon may sometimes stick or cling to the support, itself,due to surface tension between the melted silicon and the support. Toaddress this problem, in one or more embodiments, the arms 30 areconfigured to minimize physical contact between the arms 30 and thesubstrate (e.g., a silicon substrate) placed on the arms 30. Byminimizing physical contact between the arms 30 and the substrate placedon the arms 30, when the substrate is melted, surface tension betweenthe arms 30 and molten material (e.g., melted silicon) is reduced. As aresult, the molten material will be less likely to stick or cling to thearms 30 and will instead flow off of the arms 30 and in to thereceptacle 22.

FIG. 6 is an enlarged perspective view of the arm 30 of the support 20according to an embodiment of the present disclosure. FIG. 7 is anenlarged plan view of the arm 30, and FIG. 8 is an enlargedcross-sectional view of the arm 30 along the axis shown in FIG. 7. It isbeneficial to review FIGS. 6 to 8 together. The arm 30 includes a bodyportion 44 and a raised portion 46.

The body portion 44 includes a first end physically coupled to the frame26, and a second end physically coupled to the raised portion 46. In oneembodiment, as best shown in FIGS. 2 to 3, the arms 30 extend from theframe 26 towards a center of the opening 28. The body portion 44 is usedto position the raised portion 46 away from the frame 26. This ensuresthat when a substrate is positioned on the raised portion 46 and thenmelted, the melted material will not flow on to the frame 26, and willinstead flow in to the receptacle 22. The body portion 44 includes anupper surface 48 and side surfaces 50.

The upper surface 48 of the body portion 44 is a planar surface. In oneembodiment, the upper surface 48 is substantially coplanar with an uppersurface 52 of the frame 26.

The side surfaces 50 of the body portion 44 are slanted or tiltedsurfaces. The side surfaces 50 are slanted or tiled downward so thatmelted material may readily slide off of the body portion 33, throughthe opening 28, and in to the receptacle 22.

The raised portion 46 is physically coupled to the body portion 44. Theraised portion 46 is used to support a substrate within the reactionchamber 24. The raised portion 46 includes an upper surface 54 and sidesurfaces 56.

The upper surface 54 of the raised portion 46 provides a planar surfacefor substrates to rest upon. For example, as will be discussed infurther detail below with respect to FIG. 9, a silicon substrate ispositioned on the upper surface 54 during fabrication of a SiC wafer. Inone embodiment, the upper surface 54 of the raised portion 46 and theupper surface 48 of the body portion 44 are substantially parallel toeach other.

The upper surface 54 allows physical contact between the support 20 anda substrate (e.g., a silicon substrate) placed on the support 20,specifically the arms 30, to be minimized. Namely, when a substrate isplaced on the upper surface 54, the substrate will physically contactthe upper surface 54 but will not physically contact the remainingportions of the support 20 (e.g., the frame 26, the body portion 44 ofthe arms 30, and the side surfaces 56 of the raised portion 46, etc.).Thus, when the substrate is melted, surface tension between the support20 and molten material (e.g., melted silicon) is reduced. As a result,the molten material is less likely to stick or cling to the arms 30 andwill instead flow off of the arms 30 and in to the receptacle 22.

The side surfaces 56 of the raised portion 46, similar to the sidesurfaces 50 of the body portion 44, are slanted or tilted downward sothat melted material may readily slide off of the raised portion 46,through the opening 28, and in to the receptacle 22. The raised portion46 may include any number of side surfaces 56 (e.g., one, three, four,five side surfaces). For example, in the embodiment shown in FIGS. 6 to8, the raised portion 46 is pyramid-shaped with four side surfaces 56and the upper surface 54 at the apex of the pyramid. As another example,the raised portion 46 may be cone-shaped with a single side surface 56and the upper surface 54 at the apex of the cone.

The raised portion 46 lifts or raises the substrate placed on its uppersurface 54 to be above the body portion 44 and/or the frame 26. Forexample, as shown in FIG. 8, the upper surface 54 is raised above theupper surface 48 of the body portion 44 by a distance D4. In oneembodiment, the distance D4 is between 0.5 to 3 millimeters. As will bediscussed in further detail with respect to FIG. 13, raising thesubstrate positioned on the raised portion 46, specifically the uppersurface 54 of the raised portion 46, allows an etching gas to flow andcontact a lower surface of the substrate.

The support 20 may be made from a wide variety of materials. Forexample, the support 20 may be made of graphite, iron, copper,aluminium, nickel etc. In one embodiment, the support 20 is made of amaterial having a high melting temperature such that the support 20 doesnot melt when the heater 14 is on. In one embodiment, the support 20 hasa melting temperature that is greater than a melting temperature of asubstrate intended to be melted in the reaction chamber 24.

In one embodiment, the support 20, including the frame 26 and the arms30, are a single contiguous piece. For example, the support 20 may beformed from a single piece of material.

The support 20 may be fabricated using various fabrication techniques.For example, the support 20 may be fabricated by stamping a flat sheetof material using a forming press.

FIGS. 9 to 13 are cross-sectional views illustrating various stages of amethod of fabricating a wafer using the apparatus of FIG. 1 according toan embodiment disclosed herein. In the embodiments shown in FIGS. 9 to13, a SiC wafer, such as a 3C SiC wafer, is fabricated. It is noted thatthe body 12, the heater 14, the input duct 16, and the output duct 18are not shown in FIGS. 9 to 13 for simplicity purposes.

As shown in FIG. 9, a substrate of a first material is positioned on thesupport 20 and in the reaction chamber 24. In the embodiment shown inFIG. 9, a silicon substrate 58 is positioned on the support 20 and inthe reaction chamber 24. The silicon substrate 58 is positioned on theupper surfaces 54 of the raised portion 46 of the arms 30. In oneembodiment, the silicon substrate 58 has a crystalline structure. In oneembodiment, the reaction chamber 24 is at room temperature when thesilicon substrate 58 is positioned on the support 20.

Once the silicon substrate 58 is positioned on the support 20, thereaction chamber 24 is sealed and heated by the heater 14 to a firsttemperature. In one embodiment, the first temperature is between 450 and550 degrees Celsius. The reaction chamber 24 is also set to have a firstpressure level. In one embodiment, the first pressure level is between8E-5 and 12E-5 bar.

Subsequent to the reaction chamber 24 being heated to the firsttemperature, the reaction chamber 24 is heated by the heater 14 to asecond temperature that is greater than the first temperature. In oneembodiment, the second temperature is between 1050 to 1150 degreesCelsius. The reaction chamber 24 is also set to have a second pressurelevel that is greater than the first pressure level. In one embodiment,the second pressure level is between 75-125 mbar.

The reaction chamber 24 is maintained at the second pressure level forthe remainder of the process.

Subsequent to the reaction chamber 24 being heated to the secondtemperature, the silicon substrate 58 is immersed in hydrogen (H₂). TheH₂ is introduced into reaction chamber 24 through the input duct 16. Inaddition, the silicon substrate 58 is subjected to activation operationsby introducing hydrogen chloride (HCl) into the reaction chamber 24through the input duct 16.

The reaction chamber 10 is then heated by the heater 14 to a thirdtemperature that is greater than the second temperature. In oneembodiment, the third temperature is between 1340 and 1400 degreesCelsius.

While or subsequent to the reaction chamber 24 being heated to the thirdtemperature, a carbon precursor is introduced into the reaction chamber24 through the input duct 16. The carbon precursor carbonizes thesuperficial silicon atoms of the silicon substrate 26 to form a thinlayer (e.g., in the order of a few nanometers) of SiC, such as 3C SiC.This is often referred to as ramp carbonization. As will be discussedbelow, the thin layer of SiC acts as a seed for SiC growth.

Once the reaction chamber 24 is at the third temperature, a siliconprecursor is added to the carbon precursor in the reaction chamber 24.By introducing the silicon precursor into the reaction chamber 24, alayer of a second material begins to grow. In particular, a first SiClayer 60 begins to epitaxially grow from the thin layer of SiC as shownin FIG. 10. This is often referred to as hetero-epitaxial growth.

While maintaining a flow of H₂ into the reaction chamber 24 through theinput duct 16, a melting process is performed. In particular, thereaction chamber 24 is heated by the heater 14 to a fourth temperature.The fourth temperature is greater than a melting temperature of thesilicon substrate 58 and less than a melting temperature of the firstSiC layer 60. In one embodiment, the fourth temperature is between 1550to 1650 degrees Celsius. As a result, as shown in FIG. 11, the siliconsubstrate 58 melts and drains into the receptacle 22. That is, meltedsilicon material 66 of the silicon substrate 58 flows from an upper side62 of the support 20, through the opening 28, and to a lower side 64 ofthe support 20. The melted silicon material 66 of the silicon substrate58 is collected in the receptacle 22.

As previously discussed, the upper surface 54 allows physical contactbetween the support 20 and a substrate placed on the support 20 to beminimized. In this case, as the silicon substrate 58 is placed upon theupper surface 54 of the raised portion 46 of the arms 30, the siliconsubstrate 58 will physically contact the upper surface 54 but will notphysically contact the remaining portions of the support 20 (e.g., theframe 26, the body portion 44 of the arms 30, and the side surfaces 56of the raised portion 46, etc.). Thus, when the silicon substrate 58 ismelted, surface tension between the support 20 and the melted siliconmaterial 66 is reduced. As a result, the melted silicon material 66 isless likely to stick or cling to the arms 30 and will instead flow offof the arms 30 and in to the receptacle 22.

Further, as previously discussed, the body portion 44 and the raisedportions 46 of the arms 30 have side surfaces 50 and side surfaces 56,respectively, that are slanted or tilted downward. As a result, themelted silicon material 66 may easily slide off of the arms 30, throughthe opening 28, and in to the receptacle 22.

In one embodiment, the fourth temperature of the reaction chamber 24 ismaintained until all of the silicon substrate 58 is removed from thefirst SiC layer 60.

In one embodiment, the fourth temperature of the reaction chamber 24 ismaintained until the silicon substrate 58 is substantially melted andseparated from the first SiC layer 60. For example, as shown in FIG. 11,the fourth temperature of the reaction chamber 24 may be maintaineduntil small residual portions 70 (e.g., a thin layer of siliconmaterial) of the silicon substrate 58 remain on the support 20. In thisembodiment, as will be discussed in further detail with respect to FIG.13, the residual portions 70 of the silicon substrate 58 are removed bya subsequent etching process.

As shown in FIG. 12, a flow of silicon and carbon precursor isintroduced into the reaction chamber 24 through the input duct 16. Byintroducing the silicon and carbon precursor into the reaction chamber24, the first SiC layer 60 continues to grow in thickness. Stateddifferently, a second SiC layer 68 begins to grow on the first SiC layer60. This is often referred to as homo-epitaxial growth. In oneembodiment, the flow of silicon and carbon precursor is performedsimultaneously with the melting of the silicon substrate 58. In oneembodiment, the flow of silicon and carbon precursor is performed afterthe melting process of the silicon substrate 58 is completed.

When the second SiC layer 68 reaches a desired thickness, the flow ofsilicon and carbon precursor is stopped. Further, any reaction gases inthe reaction chamber 24 are removed from the reaction chamber 24 throughthe output duct 18.

As previously discussed, in one embodiment, the fourth temperature ofthe reaction chamber 24 is maintained until all of the silicon substrate58 is removed from the first SiC layer 60. In this embodiment, after thesecond SiC layer 68 reaches a desired thickness, the reaction chamber 10is shut down, vented, and returned to a lower temperature (e.g., roomtemperature). In one embodiment, the resulting SiC wafer 72 issubsequently immersed in H₂ or Ar.

As previously discussed, in one embodiment, the fourth temperature ofthe reaction chamber 24 is maintained until the silicon substrate 58 issubstantially melted and separated from the first SiC layer 60. In thisembodiment, after the second SiC layer 68 reaches a desired thickness,the residual portions 70 of the silicon substrate 58 is removed by asubsequent etching process. As shown in FIG. 13, an etching gas, such ashydrochloric (HCl) acid, is introduced into the reaction chamber 24through the input duct 16. The residual portions 70 of the siliconsubstrate 58 still coupled to the first SiC layer 60 are then removed bythe etching gas. The removed residual portions 70 of the siliconsubstrate 58 are collected in the receptacle 22. Once the residualportions 70 of the silicon substrate 58 are removed, the reactionchamber 10 is then shut down, vented, and returned to a lowertemperature (e.g., room temperature). In one embodiment, the resultingSiC wafer 72 is subsequently immersed in H₂ or Ar.

It is noted that it is possible to remove the residual portions 70 ofthe silicon substrate 58 by a subsequent etching process because theraised portion 46 of the arms 30 lifts or raises the first SiC layer 60,the second SiC layer 68, and the residual portions 70 to be above thebody portion 44 and/or the frame 26. By raising the first SiC layer 60,the second SiC layer 68, and the residual portions 70, the etching gasis able to flow to contact the residual portions 70, which arepositioned below the first SiC layer 60.

Although the apparatus 10 has been largely discussed with respect tofabricating a SiC wafer, the apparatus 10 may be used for any process inwhich a first layer of material is melted and separated from a secondlayer of material.

The various embodiments provide an apparatus and method for fabricatinga wafer, such as a SiC wafer. The apparatus includes a support having aplurality of arms for supporting a substrate, such as a siliconsubstrate. The arms are configured to minimize physical contact betweenthe support and the substrate. As a result, when the substrate ismelted, surface tension between the arms and molten material is reduced,and the molten material will be less likely to stick or cling to thesupport.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

The invention claimed is:
 1. An apparatus, comprising: a chamber; areceptacle in the chamber; a heater configured to heat the chamber; aninput duct configured to introduce a gas into the chamber; an outputduct configured to remove the gas from the chamber; and a support in thechamber and on the receptacle, the support including a frame, an openingin the frame, and a plurality of arms, each of the plurality of armshaving a fixed end and a free end opposite to the fixed end, the fixedend being attached to the frame, the free end extending in to theopening and being suspended over the receptacle, each of the pluralityof arms including a body portion and a raised portion, the body portionhaving a first end attached to the frame and a second end attached tothe raised portion.
 2. The apparatus of claim 1 wherein each of theplurality of arms extend from the frame and towards a center of theopening.
 3. The apparatus of claim 1 wherein the raised portion includesan upper surface and a plurality of angled side surfaces.
 4. Theapparatus of claim 1 wherein the frame and the opening have circularshapes.
 5. The apparatus of claim 1 wherein the receptacle includessidewalls, and the support is positioned on the sidewalls.
 6. A support,comprising: a frame; an opening in the frame; and a plurality of armsextending in to the opening, each of the plurality of arms beingcantilevered from the frame, each of the plurality of arms including abody portion coupled to the frame, and a raised portion coupled to thebody portion, an upper surface of the body portion being coplanar withan upper surface of the frame, the raised portion being positioned at aportion of the arm that is furthest away from the frame.
 7. The supportof claim 6 wherein the plurality of arms includes a first set of armshaving a first length, and a second set of arms having a second lengththat is larger than the first length.
 8. The support of claim 6 whereinthe raised portion includes an upper surface and a plurality of angledside surfaces.
 9. The support of claim 8 wherein the body portionincludes an upper surface and a plurality of angled side surfaces. 10.The support of claim 9 wherein the upper surface of the raised portionis positioned above the upper surface of the body portion.
 11. Thesupport of claim 9 wherein the upper surface of the body portion issubstantially coplanar with a surface of the frame.
 12. A support,comprising: a frame; an opening in the frame; and a plurality of armsphysically coupled to the frame, the plurality of arms extending fromthe frame and in to the opening, the plurality of arms including a firstset of arms having a first length, and a second set of arms having asecond length smaller than the first length, each of the plurality ofarms including a body portion physically coupled to the frame, and araised portion physically coupled to the body portion, the frame and theraised portion being on opposite sides of the body portion.
 13. Thesupport of claim 12 wherein the raised portion includes an upper surfaceand a plurality of angled side surfaces.
 14. The support of claim 13wherein the body portion includes an upper surface and a plurality ofangled side surfaces.
 15. The support of claim 14 wherein the uppersurface of the raised portion is positioned above the upper surface ofthe body portion.
 16. The support of claim 12 wherein the plurality ofarms extend towards a center of the opening.
 17. The support of claim 12wherein each of the first set of arms is positioned between two arms ofthe second set of arms.